Editing XML (section)

=== Valid characters ===
{{Main|Valid characters in XML}}
Unicode code points in the following ranges are valid in XML 1.0 documents:{{sfnp|Bray|Paoli|Sperberg-McQueen|Maler|2008|loc=section 2.2}}
* U+0009 (Horizontal Tab), U+000A (Line Feed), U+000D (Carriage Return): these are the only [[C0 and C1 control codes|C0]] controls accepted in XML 1.0;
* U+0020–U+D7FF, U+E000–U+FFFD: this excludes some noncharacters in the [[Basic Multilingual Plane|BMP]] (all surrogates, U+FFFE and U+FFFF are forbidden);
* U+10000–U+10FFFF: this includes all code points in supplementary planes, including noncharacters.

XML 1.1 extends the set of allowed characters to include all the above, plus the remaining characters in the range U+0001–U+001F.{{sfnp|Bray|Paoli|Sperberg-McQueen|Maler|2006|loc=section 2.2}} At the same time, however, it restricts the use of C0 and [[C0 and C1 control codes|C1]] control characters other than U+0009 (Horizontal Tab), U+000A (Line Feed), U+000D (Carriage Return), and U+0085 (Next Line) by requiring them to be written in escaped form (for example U+0001 must be written as <code>&amp;#x01;</code> or its equivalent). In the case of C1 characters, this restriction is a backwards incompatibility; it was introduced to allow common encoding errors to be detected.

The code point [[U+0000]] (Null) is the only character that is not permitted in any XML 1.1 document.